Relative to the cost of living, the pay is peanuts. You live in the GTA paying SF like rent, but paid 1/5 of the salary.
The pay is more like 40%-20% lower. Senior devs can just negotiate remote roles with US companies.
Rent in Toronto is definitely not the same as SF, even if you ignore the currency gap. Cost of living overall is way cheaper.
Toronto rent is definitely cheaper though. But probably not enough for the pay discrepancy and higher taxes